Investigations

First line investigations:

• chest radiology
• full blood count and differential white cell count
• urea and electrolytes
• sputum and blood culture - especially for pneumococcus, Mycobacterium tuberculosis
• Also pulse oximetry and/or blood gases; consider ECG and cardiac enzymes.

Further investigation:

• serology for atypical organisms - slow, but useful for:
  • Mycoplasma pneumoniae, Legionella pneumophila, Chlamydia psittacosis and Chl. pneumoniae, Coxiella burnetti, viruses
  • on admission send clotted 10 ml blood sample with a second sample 10 days later

Microbiological specimens may be necessary in patients whom fail to respond to conventional treatment - for example, bronchial washings from fibre-optic bronchoscopy, or percutaneous lung aspiration.

Some centres have countercurrent immunoelectrophoresis available for the identification of pneumococcal antigen from sputum, urine, blood, or CSF. It is not affected by antibiotic therapy.